Re: [stella] 7800 programs -- potential problems?

Subject: Re: [stella] 7800 programs -- potential problems?
From: Kevin Horton <khorton@xxxxxxxxxx>
Date: Sun, 16 Jan 2000 10:29:13 -0500 (EST)
At 01:32 1/16/00 -0600, you wrote:
>It has come to my attention that there is a dealer out there who
>believes he has gotten the rights to an encryption method to the
>7800; actually, it sounds like it might be PICKLOCK.

Well not to too my horn or anything but I have found a way around that pesky
encryption.  It involves not some software work but a piece of hardware.
I call it the "ROMblaster" because it does just that- blasts the ROM in the
7800 and temporarally over-powers it enough to get its reset vectors in
and totally bypass the 7800's ROM by overpowering it.

Circuit can be composed of a 74HC244 (enough "oomph" to overcome the cheesey
ROM's output stage) and some selection logic to detect the proper memory
range and force our code there, overpowering whatever is in the 7800.
Note this overpowering lasts only several microseconds... not enough to damage
anything or even get the chips hot.  Just long enough to switch the 7800's
BIOS ROM out... about 3 lines of code (and a reset vector).

Once this is done, the machine is ours and we don't even have to wait for
that pesky startup logo thingy, and don't have to waste ROM space with that
silly "lockpick" thingy.

A relatively simple solution to a relatively simple problem.  If you can't
work around neatly use brute force ;-).  Intrestingly a checksum/fingerprint
is used on the N64 in its lockout scheme though they wisely copy ROM to RAM
and shut off the cart bus to prevent such a "take over" from happening.

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